This application relates to a geared turbofan gas turbine engine, wherein the low and high pressure spools rotate in the same direction relative to each other.
Gas turbine engines are known, and typically include a fan delivering air into a compressor section, and outwardly as bypass air to provide propulsion. The air in the compressor is delivered into a combustion section where it is mixed with fuel and burned. Products of this combustion pass downstream over turbine rotors, driving them to rotate. Typically there are low and high pressure compressors, and low and high pressure turbines.
The high pressure turbine typically drives the high pressure compressor as a high spool, and the low pressure turbine drives the low pressure compressor and the fan. Historically, the fan and low pressure compressor were driven at a common speed.
More recently, a gear reduction has been provided on the low pressure spool such that the fan and low pressure compressor can rotate at different speeds. It desirable to have more efficient engines that have more compact turbines to limit efficiency loses.